The present invention relates to a remotely-controlled relay. FIG. 11 shows a remotely-controlled relay described in the same inventor's copending U.S. patent application Ser. No. 704,037 based on Japanese Patent Application No. 2-133027 which has the same filing date in Japan as that of the present invention. FIG. 14 shows the electrical circuit of the remotely controlled relay shown in FIG. 11. FIG. 12 shows the relevant portion of the remotely controlled relay when a main circuit is open. When an operating switch is switched to the position J shown in FIG. 14, an operating current flows through a diode D2 and a coil 6 to drive a plunger 5 in the direction of the arrow A in FIG. 12. At this time, an operating lever 28 rotates clockwise. When the plunger 5 reaches the middle of its stroke, the operating lever 28 drives at its abutment 28c the actuator 26a of a micro-switch 26 so that the micro-switch 26 is switched to have a movable contact thereof in contact with 26d. The plunger 5 further advances upwards with the aid of inertia until it is securely attracted by the upper end of a yoke 8, causing the contacts 11 and 21 of the main circuit to close.
FIG. 13 shows a relevant portion of a remotely controlled relay when a main circuit is closed. When an operating switch is switched to the position K in FIG. 14, the operating current flows through a diode D1 into the coil 6 to drive the plunger 5 in the direction of the arrow E in FIG. 13. At this time, the operating lever 28 rotates counterclockwise. When the plunger 5 reaches the middle of its stroke, the operating lever 28 drives at the abutment 28c the actuator 26a so that the micro-switch 26 is switched to have a movable contact thereof in contact with 26c. The plunger 5 further advances upward with the aid of inertia until it is securely attracted by the bottom of the yoke 8, causing the contacts 11 and 21 of the main circuit to open. In general, this type of bistable polar electromagnet device has a micro-switch that is switched at the middle of the plunger stroke. Thus, the attracting force of magnetized yoke 8 that attracts the plunger becomes increasingly stronger as the plunger becomes closer to the upper end or bottom of the yoke 8. This requires precise adjustment of the position of the micro-switch relative to the position of the plunger in its stroke where the micro-switch is switched from one contact to another. Thus, the manufacture of the relay is not easy. For sure operation of the micro-switch, a high current is run through the coil 6 so that the plunger 5 is driven by a large magnetic force to pass through the middle of the stroke with a large inertia.